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United States Patent |
5,627,870
|
Kopecky
|
May 6, 1997
|
Device for treating cerebral lesions by gamma radiation, and
corresponding treatment apparatus
Abstract
A device for treating cerebral lesions by gamma radiation, comprising an
approximately semi-spherical source-collimator assembly having a large
number of gamma ray sources associated with channels directed to the same
focal point. Each gamma ray source is associated with a group of channels
arranged in the manner of a cone, the apex of which is at the focal point.
Inventors:
|
Kopecky; Bernard (Nantes, FR)
|
Assignee:
|
ATEA, Societe Atlantique De Techniques Avancees (Carquefou, FR)
|
Appl. No.:
|
381858 |
Filed:
|
April 14, 1995 |
PCT Filed:
|
June 6, 1994
|
PCT NO:
|
PCT/FR94/00667
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371 Date:
|
April 14, 1995
|
102(e) Date:
|
April 14, 1995
|
PCT PUB.NO.:
|
WO94/28973 |
PCT PUB. Date:
|
December 22, 1994 |
Foreign Application Priority Data
Current U.S. Class: |
378/65; 378/68 |
Intern'l Class: |
A61N 005/10 |
Field of Search: |
378/64,65,68
|
References Cited
U.S. Patent Documents
4780898 | Oct., 1988 | Sundqvist | 378/65.
|
5528653 | Jun., 1996 | Song et al. | 378/65.
|
Foreign Patent Documents |
248774 | Dec., 1987 | EP.
| |
371303 | Jun., 1990 | EP.
| |
431785 | Jun., 1991 | EP.
| |
2672220 | Aug., 1992 | FR.
| |
Other References
Search Report FR 93 06787 1994.
|
Primary Examiner: Porta; David P.
Assistant Examiner: Bruce; David Vernon
Attorney, Agent or Firm: Pollock, Vande Sande & Priddy
Claims
I claim:
1. Device for treating cerebral lesions by gamma radiation, of the type
comprising an approximately hemispherical source/collimator assembly (2)
which includes a large number of gamma-ray sources (21) associated with
channels (20) which are all oriented towards one and the same focusing
point (18), characterized in that each gamma-ray source (21) is associated
with a bundle (17) of channels (20) bounded by a conical envelope of
revolution (19), the vertex of which is located at the focusing point
(18).
2. Device according to claim 1, wherein each source (21) lies opposite the
entrance opening of all the channels (20) of the bundle (17) which is
associated with it.
3. Device according to claim 1 wherein all the channels (20) are
cylindrical.
4. Device according to claim 1 wherein all the channels (20) have
substantially the same dimensions.
5. Device according to claim 1, wherein each bundle (17) includes at least
five channels (20).
6. Apparatus for treating cerebral lesions by gamma radiation, comprising a
device according to claim 1, and a movable patient-supporting table (4)
equipped with a stereotactic device (26) intended to interact with the
patient's head.
Description
FIELD OF THE INVENTION
The present invention relates to a device for treating cerebral lesions by
gamma radiation, of the type comprising an approximately hemispherical
source/collimator assembly which includes a large number of gamma-ray
sources associated with channels which are all oriented towards one and
the same focusing point.
BACKGROUND OF THE INVENTION
Gamma-radiation apparatuses have been proposed for non-invasive
neurosurgery of the brain in order to treat cerebral lesions without
opening the cranium. Destruction of the lesions is achieved by precisely
concentrating gamma radiation onto the areas to be treated, such as venous
malformations or tumors. These apparatuses are often designated by the
name "gamma surgical apparatuses" or "gamma bistouries".
In these apparatuses, external gamma-radiation sources are used, the
radiation being directed and concentrated, in a precise manner, onto the
treated lesion in order for the desired dose to be absorbed by this lesion
without appreciably damaging the intermediate tissues intervening between
the sources and the lesion, nor the tissues surrounding the lesion and, in
a general manner, reducing to a minimum the radiation doses absorbed by
the healthy tissues.
This is achieved especially by the devices of the aforementioned type, an
example of which is described in FR-A-2,672,220. In this technology, a
large number of fixed external sources are used, these being collimated
individually and arranged radially so that the axes of the rays that they
produce converge onto a focal point which coincides with the lesion to be
treated. The intensity of each beam is insufficient to damage the
intermediate healthy tissues through which it passes, especially as the
device is given, during the treatment, an angular movement about the
focusing point. In contrast, at the point of convergence or focal point,
the dose received by the lesion is sufficient to destroy it.
In this known technique, each source is associated with an at least
approximately conical single channel, the generatrices of which converge
towards the focusing point and in which a conical central needle made of a
material absorbing the gamma rays is positioned.
SUMMARY OF THE INVENTION
The object of the invention is to improve this known device so as better to
concentrate the radiation at the focusing point in order to improve the
effectiveness of the treatment, while at the same time better protecting
the healthy areas in the brain from the gamma radiation.
For this purpose, the invention is a treatment device of the aforementioned
type, in which each gamma-ray source is associated with a bundle of
channels bounded by a conical envelope of revolution, the vertex of which
is located at the focusing point.
The device may include one or more of the following characteristics:
each source lies opposite the entrance opening of all the channels of the
bundle which is associated with it;
all the channels are cylindrical;
all the channels have substantially the same dimensions;
each bundle includes at least five channels.
The invention also relates to an apparatus for treating cerebral lesions by
gamma radiation, comprising a device such as defined hereinabove, and a
movable patient-supporting table equipped with a stereotactic device
intended to interact with the patient's head.
BRIEF DESCRIPTION OF THE DRAWINGS
An illustrative embodiment of the invention will now be described with
reference to the appended drawings, in which:
FIG. 1 is a schematic overall view, in side elevation and partly in
section, of a treatment apparatus in accordance with the invention, in the
stand-by position;
FIG. 2 depicts, in a similar manner, the apparatus during treatment;
FIG. 3 is a side-on view of the source/collimator assembly indicating the
possible positions of the patient's head;
FIG. 4 is a front view of the subject of FIG. 3;
FIG. 5 depicts, in longitudinal section and on a larger scale, the region
of the source/collimator assembly associated with a source;
FIG. 6 illustrates, in perspective, the set of channels associated with a
source;
FIG. 7 is a view taken in the direction of FIG. 5; and
FIG. 8 illustrates, by means of a diagram, the energy-flux distribution in
the vicinity of the focusing point.
DETAILED DESCRIPTION
The apparatus for treating cerebral lesions, depicted in FIGS. 1 and 2, is
of the type described in the aforementioned FR-A-2,672,220. It comprises a
fixed main frame 1 in the upper part of which a source/collimator assembly
2 is mounted. Attached to this frame is a fixed secondary frame 3 which
supports a patient-supporting table 4, this being achieved by means of a
numerical-control motorized device 5 which enables the table to be moved
parallel to itself in three orthogonal directions, X (which is the
longitudinal direction of the table), Y and Z (vertical direction). The
frames 1 and 3 contain, moreover, appropriate electronic calculating means
for the control, these being shown schematically at 6A and 6B,
respectively, in order to provide the operation which will be described
hereinbelow.
The source/collimator assembly 2, which may be seen better in FIGS. 3 and
4, has a substantially hemispherical general shape. It comprises a thick
external shield 7, made of pure or low-alloy lead, the external surface of
which matches, with a small radial clearance, the internal surface of a
shell 8 of the frame 1. This shell is closed on all sides, with the
exception of a front opening 9 just sufficient to allow passage of the
table 4 supporting a patient.
Positioned in the shield 7 are, a thin source-holder 10 and, on the inside
of the latter, a thick collimator 11 defining a spherical internal surface
12. The members 10 and 11 are fixed in the shield by means of a peripheral
ring 13 which is itself held by a crimped annular flange 14.
Passing right through the central region of assembly 2, shown in the
side-on view (FIG. 3) and over a greater angular extent in the front view
(FIG. 4), is a large number of groups of radial channels. Each group
consists of a stepped outer channel 15 passing through the shield, of a
cylindrical channel 16 passing through the source holder and of a bundle
of channels 17 passing through the collimator. The axes of all these
channels converge towards a focusing point 18, which is the center of the
sphere.
As depicted in FIGS. 5 to 7, each bundle 17 is bounded by an imaginary
cone-shaped envelope 19, the vertex of which is located at the point 18.
The large base and the small base of the envelope 19, in the region of the
external and internal surfaces of the collimator 11, have, respective,
diameters of the order of 20 mm and 10 mm. The bundle 17 consists of a
certain number of fine cylindrical channels 20, all the axes of which
converge towards the point 18. The diameter of each channel 20 is of the
order of 2 to 3 mm and the number of channels in one bundle depends on the
space available in the envelope 19. This number is, for example, five or
more, as illustrated in FIG. 7.
The bulk of the collimator 11 consists of a highly gamma-ray absorbent
material, especially pure or low-alloy lead or natural uranium or uranium
depleted of isotope 235, rendered non-oxidizable by disposition of a
protective layer or by alloying, especially on the wall of each channel
20.
A caesium 137 gamma-ray source, of cylindrical shape, the diameter of which
is approximately equal to the large diameter of the envelope 19, is
arranged in the channel 16 and held in place therein by a pressing member
22 inserted into and appropriately fixed in the channel 15 (FIGS. 3 and
4).
A port 23 is mounted so as to tilt on the frame 1 about a horizontal and
transverse spindle 24 and carries a block 25 consisting of a highly
gamma-ray absorbent material, for example uranium.
The table 4 carries a stereotactic device 26 supported by uprights 27 fixed
to the table.
The operation of the apparatus will now be described.
A preliminary investigation phase has allowed the patient's head to be
positioned in the stereotactic 26 device and the lesion to be treated to
be identified in space.
For the treatment, the table 4 being removed from the frame 1 (FIG. 1), the
patient's head is firstly repositioned in the same manner. The port 23 is
then closed and is applied to the perimeter of the ring 13, and the block
25 lies at the focusing point 18 and absorbs the focused gamma rays.
Next, the port 23 is opened and the patient's head is inserted under the
collimator via the opening 9, the table being made to carry out a first
approach movement in directions X and Z and then a final adjustment
movement in directions X and Y of the order of .+-.70 mm (reference D in
FIGS. 3 and 4). This brings the lesion, identified by means of the device
26, into coincidence with the point 18. The head then lies at an
appreciable radial distance from the internal surface 12 of the assembly
2, which distance is very much greater than the dimensions of the lesion
to be treated.
Then, during the treatment, the contour of the lesion is followed by means
of small movements of the table in directions X, Y and Z, of the order of
.+-.10 mm, called treatment movements (reference d in FIGS. 3 and 4).
Simultaneously, the collimator is given an oscillatory movement, with a
small angle a of approximately .+-.5.degree., about the aforementioned
spindle which passes through the gamma-ray focusing point (FIG. 3).
The three-dimensional movement of the table 4 is very precise, of the type
used in certain numerical-control machine tools. It is controlled by a
computer, on the basis of medical-imaging data obtained using a scanner,
magnetic resonance or other techniques. It enables, from just the one
initial adjustment, arbitrarily shaped lesions to be treated very
accurately in a single operation.
The oscillatory movement of the assembly 2 enables the healthy tissues,
located between it and the focusing point, not to be damaged, and it also
enables any contact of particularly sensitive areas in the brain with the
gamma rays to be avoided.
Moreover, each surface element of the source, located opposite a channel,
emits radiation which will either be absorbed by the wall of this channel
or will pass to the point 18 or very close to it. In particular, in a
plane perpendicular to the central axis of the envelope 20, the entire
beam is concentrated onto a very small length AB (FIGS. 5 and 6). In
addition, as depicted in FIG. 8, where the cumulative energy E of the
gamma rays is plotted as ordinates and the distance d from the point 18 as
abscissae, virtually the entire energy of the gamma rays is concentrated
in the region which immediately surrounds the focal point 18, forming an
almost rectangular pulse, the energy being virtually zero at the points A
and B. In other words, a relatively narrow focal spot is obtained, which
spot typically has a diameter of the order of a few mm, especially 2 to 4
mm, and in which virtually all the gamma energy is concentrated.
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